Service after sale

I bought a Micromax canvas knight A350, with in 6 months i faced a problem so i gave my mobile to micromax authorized service center on 30th June 2015, that time service center claim to give me mobile back with in 10 days but untill now it is more then 40 days has been lapsed but they dont give my phone back and gve me time of 20 days from last 20 days. I told them that i want my phone back whether it is repaired or not but they even not giving me the details. my job sheet no is. W030242-0615-17624761